CN101365931A

CN101365931A - Ultrasensitive spectrophotometer

Info

Publication number: CN101365931A
Application number: CNA2006800079750A
Authority: CN
Inventors: D·W·拉尔森; 徐治
Original assignee: University of Missouri System
Current assignee: University of Missouri System
Priority date: 2005-01-13
Filing date: 2006-01-11
Publication date: 2009-02-11
Also published as: US7262844B2; WO2006076353A3; CA2593967A1; WO2006076353A2; US20060152726A1; JP2008537993A; EP1856492A4; EP1856492A2

Abstract

The invention provides spectrophotometer devices for ultrasensitive measurements through a reflection interaction with matter. The level of light source noise in these measurements can be reduced in accordance with the invention. Preferred embodiments of the invention use sealed housings (112, 600, 700) lacking an internal light source, and reflection based sample and reference cells. In some embodiments a substantially solid thermally conductive housing (600, 700) is used. Other features of preferred embodiments include particular reflection based sample and reference cells.; A total internal reflection embodiment includes, for example, a prism (302, 322, 622a, 623 a) including an interaction surface, a detector, a lens that focuses a beam output from the prism onto the detector, and a closed interaction volume having an inlet and an outlet for delivering gas or liquid to the interaction surface. In a specular reflection embodiment, a reflective surface (402, 422) is used instead of a prism. In a diffuse reflection embodiment a matte surface (502, 522) is used instead of a prism and the matte surface produces scattering.

Description

Ultrasensitive spectrophotometer

Technical field

The field of the invention is a spectrophotometry.Apparatus and method of the present invention may be used in all uses of spectrophotometry de termination, just, and the absorption or the scattering of measuring light in liquid, gas, solid and on their interface.Numerous spectroscopes and analytical instrument and device may be benefited from the present invention.Exemplary application of the present invention comprises: ultraviolet-visible spectrophotometer (UV-Vis), infrared spectrophotometer (IR), atomic absorption spectrophotometer (AAS) (AA), circular dichroism spectrophotometer (CD) and high performance liquid chromatograph (HPLC).

Background technology

Here the fundamental characteristics that refers to the sample of solid, liquids and gases, for whether have absorb or the certain wavelength coverage of scattering in the tendency of light.The feature tendency of absorption of sample, scattering, transmission is the basis of spectrophotometry.Exemplary application comprises the analysis of chemistry and biological sample.Other exemplary application comprises the test of artificial product test and air, quality.

Distinguish mutually for the feature that obtains sample or with other sample, quantitatively all application directions of spectrophotometry de termination are exactly the ability of digital representation sample.No matter how use, quantitatively the critical aspects of spectrophotometry de termination is sensitivity, degree of accuracy and accuracy.The sensitivity of spectrophotometry directly with detect nuance between the sample that similar absorption characteristic is arranged ability relevant, sensitivity is high more, and is can detected difference just more little.The degree of accuracy of spectrophotometry can be thought with relevant in the ability that different time repeats same measurement to same sample.It is relevant with the numerical measuring of correct definite sample composition that the accuracy of spectrophotometry de termination can be thought.For example, when the unknown element attempting to quantize in sample, the latter is crucial.On the concentration of whole given range, remove to characterize quantized value by the degree of accuracy and the accuracy of certain level.Yet, be lower than concentration range following in limited time, degree of accuracy and accuracy meeting are subjected to negative effect.This lower limit is exactly the detectability of concrete spectrophotometer.Along with sensitivity improves, detectability just reduces.Yet, improve sensitivity, keep high-caliber degree of accuracy and accuracy simultaneously, this is that people wish.

We before provided and had used the sensitivity that transmissometry improves spectrophotometry de termination.Our U.S. Patent No. 6,741,348 (' 348 patents) method and apparatus that super-sensitive spectrophotometry de termination is provided is disclosed.

Summary of the invention

The present invention expands to other measurement range with the measurement capability of ' 348 patent, wherein, light and matter interaction, thus intensity variation caused.The luminosity spectrometer device of the preferred embodiments of the present invention provides overdelicate measurement by interacting with the material reflection.According to the present invention, can be reduced in the level of light source noise in these measurements.The preferred embodiments of the present invention are used the seal casinghousing of no internal light source and based on the reflection of sample chamber and reference chamber.In certain embodiments, use the housing of solid basically heat conduction.Device of the present invention uses has the twin-beam structure of sample beam and reference beam.Described twin-beam is produced by same light source, thereby, the experimental noise relevant with light source, that is, comparatively faster random fluctuation and slower drift coherently appear in the two-beam.In an embodiment of the present invention, can use the technology that disappears mutually and improve sensitivity by reducing the coherent experimental noise level.The further feature of preferred embodiment comprises the specific reflection based on sample chamber and reference chamber.For example, total internal reflection embodiment comprises: prism, and it has interaction surface; Detecting device; Lens are used for the light from prism output is focused on detecting device; And airtight interaction volume, it has outlet and inlet, so that analyte is sent to interaction surface.In direct reflection embodiment, use reflecting surface to replace prism.In diffuse reflection embodiment, use material surface to replace prism.The present invention also comprise each parts of the generation noise of identification in the spectrophotometry de termination and select to be provided with the preferred feature among the given embodiment, in the application of the device of preferred embodiment, can realize very noise level near the shot noise limit.

Description of drawings

For a person skilled in the art, by reading the detailed description with reference to accompanying drawing, other features, objects and advantages of the present invention will be apparent, wherein:

Fig. 1 is the spectrophotometric vertical view of removing cover plate of preferred embodiment;

Fig. 2 A, Fig. 2 B, 2C illustrate the detector circuit of preferred embodiment;

Fig. 3 illustrates the spectrophotometric part of total internal reflection of preferred embodiment;

Fig. 4 illustrates the spectrophotometric part of direct reflection of preferred embodiment;

Fig. 5 illustrates the spectrophotometric part of preferred embodiment diffuse reflection;

Fig. 6 is the spectrophotometric vertical view of the total internal reflection of removing cover plate of another preferred embodiment; And

Fig. 7 is the spectrophotometric vertical view of the diffuse reflection of removing cover plate of another preferred embodiment.

Embodiment

The present invention mainly is intended to improve the sensitivity of luminosity spectroscopic measurements method.Aspect widely of the present invention comprise each parts of the generation noise in the identification luminosity spectroscopic measurements method and selection be provided with the preferred feature of given embodiment.Some embodiments of the present invention realize reducing anti noise by combination various aspects of the present invention (promptly at each scheme of the noise source of all identifications).In these preferred embodiments, only after all important noise sources were identified and are minimized, this reduction just was considered to realize.The preferred embodiments of the present invention can produce very the noise level near the shot noise limit.The technician is by understanding additional aspect of the present invention with reference to preferred embodiment.

The invention provides the method for measuring potential interference, these interference are owing to the gas on the beam path carries particle, the reflection and the other factors on bubble in the liquid just studied and suspended particle, photodetector surface cause.These light sources are associated in the conventional equipment of required sensitivity can not providing, do not consider this noise source usually.

Apparatus of the present invention are used has the twin-beam structure of sample beam and reference beam.Twin-beam is produced by same light source, thereby, the experimental noise relevant with light source, that is, comparatively faster random fluctuation and relatively slow drift coherently appear in this two-beam.The technology of disappearing reduces the level of related experiment noise by using mutually, thereby improves sensitivity.Sample beam and reference beam be the induction light electric current on sample detector and reference detector, and, by using suitable electronic circuit and measuring poor (I between sample photocurrent and the reference photocurrent _S-I _R) eliminate to be concerned with and fluctuate.Circuit output is by the given differential voltage V of following formula _D:

V _D＝K _D(I _S-I _R) (1)。

K _DIt is the proportionality constant of determining by the parameter of electronic circuit.As photocurrent I _SAnd I _RWhen identical, at differential voltage V _DMiddle elimination appears at the relevant random fluctuation of the light source in this two-beam equally.Though at baseline V _DThe middle influence of eliminating light source drift, but they influence peak heights really.For proofreading and correct this influence, V _DDivided by by the given output reference voltage V of following formula _R:

V _R＝K _RI _R (2)

K _RBe by the determined proportionality constant of electronic circuit parameter.Light source drift influences I simultaneously _SAnd I _RThe two, this passes through V from formula (1) and (2) as can be known _DDivided by V _REliminate light source drift.

V _D/V _R＝K _D/K _R[I _S/I _R-1] (3)

According to formula (3), can ratio calculated I _S/ I _R:

I _S/I _R＝V _D/V _R(K _D/K _R) ^-1+1 (4)

At last, according to expression formula A=-log (I _s/ I _R), by I _S/ I _RExperiment value can calculate absorptance A.Transmissometry is the method that typically is used for analyzing true solution.In true solution, analyte disperses with the level of molecule.Therefore true solution visually is transparent, and the light of immeasurablel amount is by the scattering of (for example) suspended particle, when light during by this solution the reduction of light intensity mainly be because the absorption of light causes.In device of the present invention, can measure the absorptance of pure solution and utilize the Beer-Lambert law to analyze data with the degree of accuracy that improves greatly.

The spectrophotometer of exemplary transmission embodiment shown in Fig. 1, this spectrophotometer are used for describing some the basic noise reduction aspects among the reflection embodiment that is applied to shown in Fig. 2-7.In the structure of Fig. 1, rely on transmission, light is directly by sample, because the interaction of light and sample, light intensity is lowered.For optically transparent sample,, the absorption described in the patent reduces owing to causing light.In transmissometry, owing to there is macroscopical suspension structure body of scattered light, light intensity also can be lowered.These suspending liquid are usually expressed as cloud form, and the method that is used for its analysis is called as " turbidimetry ".Mathematical relation between the reduction of light intensity and the amount of the analyte in the suspending liquid obtains by experience.Can not use the Beer-Lambert law.Yet this method is useful, and is used routinely.Turbidimetry and other transmission are used also and can be realized with the method for Fig. 1, described in ｀ 348 patents.

The optical measuring method of second general type is reflection, and the exemplary means shown in Fig. 2-7 expands to the sample that detects better with reflection measurement with the hypersensitive transmissometry principle of Fig. 1 embodiment.Provide embodiment respectively at internal reflection, direct reflection and diffuse reflection, the technician understands aspect widely of the present invention with reference to these embodiment.

Set about introducing the transmission embodiment of Fig. 1 now, Fig. 1 constructs as experimental prototype.The spectrophotometer of Fig. 1 is implemented many aspects of the present invention, comprises the identification of noise source and is used for determining the method for the position of noise source.All embodiment provide the framework of usefulness, can understand wider and can be applicable to various aspects of the present invention outside Fig. 2-7 preferred embodiment than Fig. 2-7 preferred embodiment so that the technician to be shown.Be diagram simply, Fig. 1 preferred embodiment devices is single wave length filtering unit of working in the visible-range in incandescent source (tungsten lamp).

Overall light beam path in Fig. 1 preferred embodiment is the typical twin-beam structure that is used for spectrophotometer.(for example, tungsten lamp) light is sent on the instrument by photoconduction 108 (being preferably optical fiber) through two broad band optical filters 104,106 from 102 light sources.Photoconduction 108 has low thermal conductivity, thereby, avoid transferring to this device from the heat of light source, and attached with the assembly parts 110 of sealing.Assembly parts 110 are sealed, enter housing to prevent dust and veiling glare.Assembly parts 110 directly are attached on the inside surface of housing wall 12.

This can isolate light source 102.Specific application is depended in concrete selection to light source type.The present invention can implement to far overall optical spectral limit in ultraviolet, also can select light source suitably.Additional exemplary suitable light source comprises following light source: argon lamp, xenon lamp, hydrogen lamp, deuterium lamp, tungsten lamp, arc lamp, hollow cathode lamp, Nernst glower, nickel-chrome filament, Globar, laser instrument.Light source 102 is placed on the outside in the mode with spectrophotometric other parts heat isolation of preferred embodiment.

The common generation of light source can be transferred to the big calorimetric on spectrophotometric each opticator and the detector portion.Minimized for the conduction heat that will transfer on the instrument, thermal light source 102 is placed on the outside, thereby allows advection heat to transfer to environment on every side.In addition, heat insulation layer 113 makes that to transfer to preferred spectrophotometric heat from surrounding environment

minimum.Wave filter

104 and 106 preferably includes ultraviolet cut-on wave filter and infrared cutoff filter, and the energy range of transmitted light is narrowed down, produce thus " cold light ", and the restriction radiant heat transfer.

Preferred fibre-optic light guide 108 has position and the very sensitive polarization ratio of curvature to fiber cores.Guide fiber optic cable 108 is attached on the assembly parts 110, and these assembly parts 110 comprise the holographic diffuser 114 that reduces polarization and the actual light source diameter is reduced to the hole 116 of the size of (for example) 1/8 inch, to aim at better and to focus on.

Output beam 118 is through second hole 120 on the wall 122, and the biconvex lens 124 of being constructed with the conjugate ratio of 1:1 is assembled and focused on again.After the interfere type wave filter 126 on the wall 128, arrowband output beam 130 is by the collimation lens 132 of plano-convex, thus generation collimated light beam 134.The diameter of collimated light beam 134 is designed to littler than the open optical aperture of lens 144,146.Lens 124,132 are placed on respectively on the optical branch gripping member that is installed on the commercialization on the heat conduction assembly parts 123,135.Assembly parts have big thermal capacitance.Solid metal block is preferred for these assembly parts.

Dielectric beam splitter 136 produces transmission (sample) light beam 138 and reflection (reference) light beam 140 along path separately, and the described folded light beam mirror 142 that further is reflected reflects.Beam splitter 136 is placed on the brass supporter of our production, and catoptron 142 is kept by the adjustable supporter of commercialization, and beam splitter 136 and catoptron 142 are supported by optical building elements 137,141 respectively.These assembly parts have the structure similar to assembly parts 123,135, have big thermal capacitance.Dielectric beam splitter 136 has the Polarization-Sensitive beam separation ratio to incident light 134.For example, the dielectric beam splitter to average 60% transmission, 40% reflection only has 42% transmissive to the S polarized light, and the P polarized light is only had 76% transmissive.From the only partial polarization of monochromator or optical fiber output, the polarization ratio depends on thermal drift and mechanical drift.In exemplary experimental prototype of the present invention, optical fiber 108 has 3/8 inch core diameter.Polarization comparison fiber cores position and curvature are very responsive.Variation under the room temperature is easy to cause that the relative mistake component voltage compares V _D/ V _R10 ^-5Or the variation of the bigger order of magnitude, V _D/ V _RIt is unbalanced measurement between the two-beam.Light process holographic diffuser 114 from optical fiber output has reduced by 100 times with the polarization ratio.Therefore, polarization is basically by complete disturbance, and beam separation is than the influence that more is not vulnerable to thermal drift, thereby improved differential stability.The inventor finds that also the traditional glass scatterer with rough surface is invalid, because it can not provide sufficient polarization scrambling.

Sample beam 138 and reference beam 140 are through the condenser lens 144,146 on the wall 148, and the light beam 150,152 of line focus enters sample chamber 154 and reference chamber 156 respectively.Sample chamber 154 is in compartment 160e, and reference chamber is in compartment 160d.These two chambers are separated by wall 162.All thermally-stabilised features and the optical system that generally includes dielectric beam splitter 136 by preferred embodiment are easy to generate the balance light beam.For helping this two-beam of balance, the power of reference beam 152 also preferably can be subdued by the attenuator 164 of regulating pinpoint accuracy.Attenuator comprises assembly parts 166, precision michrometer-type screw 168 and thin bar 170.Light beam continues by being installed in the condenser lens 172,174 on the wall 176, and the detecting device 178,180 that is installed in respectively on the heat conduction chamber 182,184 collects, and detecting device is preferably chamber 182,184 in and incident light installation at 45.Like this, caught by indoor ligh trap 194,196 respectively by the light beam 186,188 of detecting device surface reflection.Photodiode detector produces the photocurrent that is supplied to detector circuit 189.Suitable detecting device will produce and the power of input (sample or with reference to) light beam electric current of proportional variation accurately.Optionally available detecting device comprises in addition, and for example: photomultiplier, photoelectric tube, photoelectric cell, electric charge shift conductor, thermopair, bolometer, thermoelectric cell and infrared detector.Circuit produces output voltage, output voltage by housing 112 be supplied to digital quantizer 190 and analysis circuit 192 (as, can realize with computing machine).

Thermally conductive pathways is based upon in the internal part by the pedestal (not shown) with big thermal capacitance.In the experimental prototype according to the transmission-type arrangement shown in Figure 1 of ' 348 patents, pedestal is 3/4 inch a solid steel, and assembly parts/chamber 123,135,137,141,154,156 and various wall and shell body are directly mounted on it.The outer wall 112 of pedestal, unshowned top cover and housing forms the hot shifting circuit of conduction with internal part.Top cover, pedestal and wall 112 provide for example 1/2 inch commercial device 113 and environment isolation.Extenuated the response of internal temperature like this to outside environmental change.Internal thermal conductivity promotes the thermal equilibrium between the internal part.

The preferred embodiment detector circuit is shown in Fig. 2 A.In accordance with the preferred embodiment the exemplary experimental prototype circuit of Fig. 2 A (top) by cheap, can form by commercially available parts.

In Fig. 2 A, from sample (S) photodiode 178 and with reference to (R) photodiode 180 (Fig. 1) electric current respectively as constant current source 200,202.Photodiode is constructed like this, makes the difference of its photocurrent appear on the node 204.Converter 208 (comprising A208, R208 and C208) converts sample photocurrent 200 to voltage, and this voltage is supplied to the end of pot P209.Converter 210 (comprising A210, R210 and C210) converts reference photocurrent 202 to voltage, and this voltage is supplied to the other end of pot P209.Bear from the voltage of converter 208 outputs, and the voltage of exporting from converter 210 is positive, so whole pressure reduction falls on P209.This voltage changes with the direct supply of light source, also comprises the noise and the drift part of light source.From the polarity of voltage of P209 output and size with potentiometric change in location.For example, voltage can be from KV _R(being positive) passes 0 to K ' V _S(bearing) changes continuously.Constant is K=R212/R210 and K '=R212/R208.Be fed back to node 204 with current forms by feedback resistor R211 from the voltage of P209 output.Feedback current is the tracking illumination source power accurately, and its size and polarity are by the value decision of several parts (R208, R210, P209, R211).Therefore, feedback current is in node 204 additions, and to increasing the big or small influential of S photocurrent or R photocurrent, this depends on the setting of P209.In this is provided with, utilize pot P209 carefully to regulate feedback current, make S photocurrent and R photocurrent reach balance, so that can eliminate source noise with certain degree of accuracy.If the S photocurrent is bigger than R photocurrent, regulate P209 so, to provide required positive potential output, vice versa.Selected component values will make the feedback current size to fit, makes S photocurrent and R photocurrent reach balance.Required feedback current can be littler by 1% than S photocurrent, and can be easy to cause that the small imbalance of photocurrent is (as 10 ^-5).Because the elimination degree of source noise equates with the degree of unbalancedness of photocurrent in the circuit, so 10 ^-5The uneven just pleasure trip on foot of photocurrent to allow to reach the detector shot noise performance.10 ^-3The shot noise of the uneven sufficient to guarantee restriction of photocurrent.

For the measurement of single wavelength, detector current must be at first by the solvent balance in sample chamber and the reference chamber.After this, the analytic sample in the measuring samples chamber.Because only requiring adjustment, P209 one time can be the simple potential meter shown in Fig. 2 A, Fig. 2 B.Yet the same with scanning element for the absorptiometry of carrying out on whole wavelength coverage, detector current must be with the solvent balance in sample chamber and the reference chamber in a plurality of wavelength.To each wavelength, this requires the difference setting of P209 usually, therefore, when the analytic sample on the spectral scan sample chamber, must change the setting of P209 before each data point of scanning survey.Each P209 is provided with and guarantees that the value in certain wave strong point balance is consistent.In order to realize this, P209 can be replaced by computer-controlled digital potentiometer, and the setting of each wavelength all is stored in the storer.

Under equilibrium condition, the input total current of differential amplifier 212 is near 0, and eliminated source noise.Source noise is eliminated at node 204 with current system, so S photocurrent and R photocurrent directly subtract each other.Then, this difference is converted into output voltage on differential amplifier 212 (comprising A212, R212, C212, D212).This is simple and the most accurate method.For producing and output differential voltage GV _D, the output of differential amplifier 212 is supplied to the additional voltage amplifier 216 of gain for G by low-pass filter 214 (comprising R214, C214).Output voltage GV _DStandard deviation determine by the shot noise of detecting device, rather than determine by foregoing noise source.

Among Fig. 2 A, Fig. 2 B, source noise is eliminated by current-mode.In addition, also can eliminate with voltage mode.The voltage mode noise cancellation detector circuit of preferred embodiment is shown in Fig. 2 C.Source photocurrent from photodiode 200 is converted to voltage by converter 220 (comprising A220, R220, C220).Output voltage V _S=I _SR220 is supplied to variable pot P220, and potentiometric output is supplied to the non-inverting input of amplifier A224.Similarly, be converted device 222 (comprising A222, R222, C222) from the reference photocurrent of photodiode 202 and convert voltage to.Output voltage V _R=I _RR222 is supplied to variable potentiometer P222, and potentiometric output is supplied to the inverting input of amplifier A224.In the structure shown in Fig. 2 C, V _SAnd V _RAll be positive.Therefore, when two input voltages of amplifier A224 equate, realize noise removing.At first, P220 and P222 produce equalization, so that there is not voltage attenuation to the maximum value of setting by being set.Regulate then and big output voltage V _SOr V _RCorresponding pot, A224 is output as till 0 up to amplifier.For example, if V _S＜V _R, P220 is set to maximal value usually, and is corresponding with FP220=1, for balance, regulates P222, corresponding with FP222＜1.FP220 and FP222 are potentiometric decay fraction, and scope is 0 to 1.Then, the coherent source noise is eliminated in the voltage difference that is exaggerated device A224 output.The output of A224 is exported by buffer amplifier A228 at last by low-pass filter 226 supplies.Eliminate about voltage, voltage difference is defined as V _D=(FP220V _S-FP222V _R), output voltage is GV _D, G is the synthetic gain of amplifier A224 and A228 here.Output voltage FP220V _SAnd FP222V _RAlso be variable.One of these outputs require to calculate absorptance by following description.

To the measurement of big absorptance, do not need noise removing, just can be directly obtain transmissivity from 208,210 output.For big absorptance, diode D212 has limited the output voltage to differential amplifier 212.This has just controlled the relevant interference of drift in the output with differential amplifier 212.In experimental prototype devices, observe, the following period of time after differential amplifier produces output voltage, it is drifted about, and this has disturbed the little V that accurately measures output terminal 216 _DValue.

When | V _R| | V _S| the time, measure absorptance and require to measure Q=V _D/ V _R+ 1; When | V _R|＜| V _S| the time, absorbance determination requires to measure Q=[1-V _D/ V _R] ^-1V _DBe 216 output voltage gain G divided by amplifier 216, V _RBe 210 output value divided by factor K, V _SBe 208 output divided by factor K ' value.V _D, V _S, V _RBe the output voltage that separates, therefore, can measure V simultaneously _DAnd V _S(or V _R), with the error of avoiding causing owing to light source drift.Because V _DAnd V _R(or V _S) all directly proportional with source power, drift that therefore must the consideration source power.If do not measure V simultaneously _DAnd V _R(or V _S), owing to measure the change of the interior source power of time of two voltages, their ratio will change.Yet, to measure at the same time down, the correlativity of source power disappears.

Voltage cancellation circuit shown in Fig. 2 C, Q is generally defined as Q=V _D/ FP222V _R+ 1.Decay fraction FP222 is a constant, FP222V _RCan be considered to effective output of amplifier A222.

The correction that detector circuit carries out is to finish under optics evener auxiliary, the optics evener can be placed in reference beam or the sample beam, or all place in two-beam.All optical designs should guarantee that light beam is near balance.Preferable feature has also been introduced balance adjustment with the fine setting beam balance.If near balance, there is the optimal way of two adjustment degree in light beam in all unit design.At first, the attenuator 164 (Fig. 1) on the wall of being installed in that can slacken reference beam is arranged in the reference light path.In this exemplary prototype, wall accessory 166 is installed 1/4-40 mechanical screws 168.Screw rod 168 is installed near the beam edge, perpendicular to beam direction the axle.The screw rod end is the little bar 170 of diameter 1mm, long 5mm.The position of thin bar can accurately be regulated by the micro screw screw thread.Screw rod can only coarse adjustment, is used for balance photocurrent i _SAnd i _RTo about 1/10 ³Secondly, be input to 212 photocurrent and can be put 0 (Fig. 2) by electronics, as mentioned above by adjusting pot P209 (Fig. 2).Utilize electronic adjustment capability, photocurrent can be balanced to 1/10 ⁵Below.Time constant by making feedback cycle and detecting device rise time are approximate, can reduce the tracking error of little balanced balanced current.Except that electric current (＜2%) in a small amount was provided by R211 very, arbitrary detector current can not be subjected to slacken the influence of the electronic filter of high-frequency component source noise.This need to have guaranteed the quick response of accurate noise removing.In addition, most of detector current can not flow through any electronic component.At last, by big relatively resistor R 211 is set, the additional noise that the resistance that exists in the input circuit by differential amplifier causes is very little, and test finds to be lower than detector shot noise.By electronics accurate balance light beam, the output of differential amplifier 212 is very little, at the order of magnitude of 10 μ V.

Circuit shown in Fig. 2 A is suitable in the scanner, and when obtaining data, light wavelength changes continuously.Before discontinuous wavelength is done measurement to each, must carry out balance to light beam by above-mentioned method.Change on the wavelength coverage of scanning owing to wish the relative power of sample beam and reference beam, therefore, be desirably in the ability that comprises the symbol that changes feedback current in this circuit.Second preferred embodiment detector circuit is shown in Fig. 2 B, and wherein, common element uses the reference number mark of Fig. 2 A.This circuit is applicable to when filter joint in the unit of single wavelength operation.Such instrument owing to only use a wavelength measurement, therefore needn't change the symbol of feedback current.Select by switch 206 from the balanced balanced current of sample or reference beam acquisition among Fig. 2 B, therefore,, in any given time, only have the unipolarity electric current to use according to the setting of switch 206.

Our experimental study finds that after noise source was eliminated, thermal drift became main factor.Therefore, another aspect of the present invention is the thermal drift of restriction differential light power ratio.Preferably, when obtaining data, with the thermal drift Δ P/P in the different luminous power ratios _R=(P _S-P _R)/P _RBe limited in 10 ^-6Below, the time of obtaining data is 15 minutes in practical application of the present invention or others.The relative mistake component voltage compares V _D/ V _R=(V _S-V _R)/V _RBe Δ P/P _RThe experiment measuring value, therefore, what experiment was paid close attention to is the stability of differential voltage.Discern and select a plurality of design features, to limit thermal drift and to guarantee high differential stability.Particularly, in measuring phases, reduce temperature drift, thereby the thermic among first embodiment changes V _D/ V _RShould be equal to or less than 10 ^-6The order of magnitude.This is consistent with the overall noise in the detector shot noise limit.When hope measures 10 ^-6During the optical power change of the order of magnitude, the preferred selection of identification coefficient given below seems very important.Because these factors are to detecting 10 ^-4Or the influence of the ability of the variable power of the bigger order of magnitude is very little, does not therefore generally understand the importance of thermal stability.The analysis of thermal drift need be used a plurality of hot coefficients.Known literature value is used as hot coefficient; Perhaps, we have carried out rational estimation to these coefficients.In some cases, obtain required coefficient by direct measurement.In order to use the optimization of luminosity spectrometer according to the present invention, this part primary aspect of the present invention relates to selection of components.

Beam splitter 136 is to produce the instable most probable optical element of difference.Except that the polarization of incident ray 134, splitting ratio is also very sensitive to incident angle and light wavelength.Incident angle and V _D/ V _RRelation be 6 * 10 ^-3/ degree.This means incident angle only 0.001 the degree variation will cause V _D/ V _RAbout 6 * 10 ^-6Variation.The distortion of expansion that temperature causes and beam separation bearing is easy to cause the subtle change of incident angle.In fact the size of all changes depends primarily on the structure and material of beam splitter assembly parts.The relatively large assembly parts of being made by solid steel block 137 provide thermal stability and mechanical stability.In the transmissivity experimental prototype, the beam splitter assembly parts are high by 3 ", wide by 3 ", thick 1/2 " copper coin.

The temperature coefficient of the interaction filtrator 126 that uses in exemplary experimental prototype is 0.023nm/ ℃, yet, for dielectric beam splitter 136, wavelength and differential ratio V _D/ V _RRelation be 5 * 10 ^-4/ nm.Here provide recombination coefficient 1 * 10 ^-5/ ℃.

Variation of temperature causes the variation of the reflectivity of beam splitter 136, and then causes V _D/ V _RSubtle change, during 45 ° of incident angles about 6.2 * 10 ^-6/ ℃ variation.This is that the change of refractive of the optical material of the use that caused by temperature causes.

Temperature variation also can cause the variation of the dark current of two detecting devices 178 and 180.In Fig. 2 A, Fig. 2 B under the structure of preferred embodiment detector circuit, detecting

device

178 and 180 dark current tend to subdue.Because reducing, unmatched detecting device eliminates effect, so detecting device preferably mates.Under more serious mismatch situation, remaining dark current can arrive 150pA.The temperature coefficient of dark current is 115%/℃, this can change 172pA/ ℃ in the difference dark current.In example experiment embodiment, photocurrent is the magnitude of 2.0 μ A.Therefore, compare V in the relative mistake component voltage _D/ V _RIn, the detecting device dark current produces 8.6 * 10 ^-5/ ℃ the potential drifting rate.

According to experimental observation and consider and measure the required reasonable time (reaching 15min), the optimization aim of preferred embodiment design is proposed.The inventor estimate with measure 1 * 10 ^-6The maximum heat drift rate of the permission of AU unanimity approximately is 0.001 ℃/minute.The temperature drift rate that is equal to or less than this level can obtain according to the preferred embodiment shown in Fig. 1-7.

Another aspect of the present invention is the thermal stability of element.Main passive thermal stability in the embodiment of the invention has two aspects.In housing, element is made by the material of high heat conductance, for example, and solid aluminium, steel, copper and other metal.Heat transfer between inner member promotes the thermal equilibrium in the embodiment of the invention.Insulating with external environment condition is on the other hand, protects instrument to be subjected to the influence of environment by the response that slows down device.Provide the strong back of big thermal capacitance, for example, 3/4 inch strong back that thick corrosion resistant plate is made is as inner member heat transfer basis.Big optics of metals assembly parts also provide big thermal capacitance and mechanical stability.Be directly installed on thick about 3/4 on the base plate " the solid steel block assembly parts provide stability, for example, whole housing can come thermoshield with the commercial isolated material of 1/2 inch of one deck.

Compartmentization in a preferred embodiment has multiple benefit, the reduction that these benefits are direct or indirect the easy-suffering level of thermal drift.The compartment permission is installed in some optical elements on the housing wall, and housing wall has good thermo-contact and thermal stability.Wall 122,128,148,162 and 176 makes Fig. 1, the easier realization of the target of 3-5 embodiment.In Fig. 6,7 embodiment, obtain good thermo-contact and thermal stability with the solid substantially housing of one.Secondly, it allows sample chamber and reference chamber to isolate light, and this has reduced the problem relevant with scattered light.In addition, the inside surface of wall and housing preferably is coated with one deck light absorbent, for example, and coarse black paint.

Lens, light filter and catoptron, for example, 114,124,126,132,142,144,146,172 and 174, be configured to resist the performance change that temperature variation causes.The assembly parts of optical element are solid, big.Large scale guarantees the stability of opposing thermal expansion.For reducing the current potential thermal drift, the supporter of beam splitter can be made by very thick and heavy material, for example, and 3 square inches, 1/2 inch thick solid metal.In 15 minutes, can make the difference drift that causes by beam splitter be lower than 1 * 10 ^-6, perhaps can make the difference drift that is caused by beam splitter is 6.7 * 10 ^-5/ ℃.

Typical silicon photodiode detector (400-750nm) in visible-range has the reflectivity near 20%.Catching reflected light from detector surface thinks useful.Produce undesirable reflection and scattering to sample supporter 154 or with reference to the light of supporter 156 reverse transfer.If allow the reflected light reverse transfer on sample or reference chamber supporter 154,156, so, between chamber, lens and detector surface, produce repeatedly reflection.Under repeatedly reflecting, can cause that any any small thermal distortion of reorientating of any of these element can stop detection 10 ^-6The light of magnitude changes.In transmission embodiment, the reflection luminous energy on control detection device surface addresses this problem.The optimal way of control reflection comprises aims at the surperficial angled of sample detector 178 and reference detector 180, and this angle is not orthogonal to incident light.

In a preferred embodiment, the incident angle on the detecting device is 45 degree, thereby catoptrical transmission direction is 90 degree with respect to incident

light.Detector compartment

182 and 184 is the installation and measuring device at a certain angle, and direct reflected

light

186 and 188 enters

ligh trap

194 and 196 respectively.Can use and can direct light enter the lower limit of ligh trap and allowing any angle between the upper limit that all light are collected by detecting device.These ultimate values will be by the sectional area decision of light beam and detecting device.Reflected

light

186 and 188 is caught by

ligh trap

194 and 196, the blacking of ligh trap inside surface.Think and catch reflected light to determining less than 5 * 10 in detector surface ^-5The absorptance of AU is important.

The pollutant or the particle of any kind on sample or reference light path all will cause interaction.Pollutant here and particle have determined to comprise for example bubble, dissolved gases and dust.For example, if approximately be 5mm at the beam cross section of sample area ²(according to the exemplary prototype of first embodiment), so any cross section is greater than 5 μ m ²Or the particle that diameter surpasses 2.3 μ m can cause greater than 1 * 10 ^-6The noise peak of AU.In our research, find, cause that the airborne particle of floating over of problem usually can be after close chamber sinks to the bottom, sample chamber in 20 minutes.The existence of lithometer can be depicted as a series of forward spike in the detector signal in the sample beam.After particle sank, dust peaks had the tendency of reduction in time.On the other hand, because Brownian movement, the particle in the liquid will just can deposit at the bottom of the chamber by good several hrs usually.In addition, any variation of temperature will recover their motions in the whole liquid chamber.This is the serious problem that detects very little absorptance in the fluid sample.In our test, these particles are easy to cause up to 5 * 10 ^-5The noise of AU.

Determine that in test process because airborne dust, traditional test tube structure that plug is arranged is not suitable for determining to be lower than 5 * 10 ^-5The absorptance of AU because clean this chamber or change liquid whenever grit can both enter test tube.In addition, open the sample chamber and airborne particle can be introduced optical system.Preferred bore hole on solid metallic object is as the fluid passage and the hole of necessity.Except dust problems, the inventor has also discerned additional possible noise source.For example, the temperature of fluid temperature under definite research and chamber has the difference in several years.The thermal conductivity of normally used quartz chamber is less relatively, therefore the temperature that often needed 5 minutes or came stable liquid for more time.Another aspect of the present invention solves the possible noise that the variation by dust/particle and room temperature causes.

The reflection measurement method and apparatus of exemplary embodiment is according to the modification of Fig. 1 embodiment.Fig. 3 illustrates the modification part of Fig. 1 embodiment, measures for carrying out internal reflection, replaces the transmission chamber 154,156 among Fig. 1.This requires different chambers, and positioning detector again.

In Fig. 3, sample beam 300 enters internal reflectance optical device, for example, and prism 302 or other internal reflectance optical device.Light is mapped to interaction surface 304 by prism 302, and light is by total internal reflection there, thereby light beam 306 penetrates from prism 302.In this process, the direction of light beam changes 90 °, but this angle only is exemplary, and the variation of other direction also can be used.Folded light beam 306 is focused on by lens 308 and is installed on the indoor sample detector 310, and this chamber is to comprise ligh trap 311 with reference to figure 1 described (out of plumb).Analyte (sample) on the interaction surface 304 of prism, when light beam on surface 304 during total internal reflection, the actual very little distance of analyte (so-called fast subwave) that penetrates of light.Penetration depth approximates light wavelength greatly.Because light penetrates sample, beam intensity is owing to absorbing or decaying with other takes place for sample on the surface 304 interaction.The degree of light intensity decays depends on the chemical characteristic of sample, and can be used to analyte quantification.By sampling receptacle 314 sample is put into surface 304 with inlet 316 and sealing of outlet 318, entrance and exit links to each other with the outside surface of housing, just analytic sample can be put into the sample chamber to allow not exclusively to open whole housing, open whole housing and will introduce the baseline noise relevant with air borne dust.

Similar with sample beam, reference beam 320 enters prism 322, and the interaction surface 324 of the prism that is reflected out.Outgoing beam 326 is focused on the reference detector 330 by lens 328, as, photodiode, reference detector 330 are accommodated in and contain the indoor of ligh trap 331, and install with non-perpendicular angle.Reference substance is placed in the container 334 that is provided with the inlet 336 and the interaction of the sealing of outlet 338.Reference beam is the same with the characteristic that takes place on interactional characteristic of the reference substance on the reference interaction surface 324 and sample interaction surface 304.

The signal of sample and

reference detector

310 and 330 is transferred to detector circuit 340 by

signal wire

312 and 332 respectively, and in example embodiment, detector circuit is the same with Fig. 2 A or 2B detector circuit.Output by sample thief detecting device 310 and reference detector 330 is poor, can eliminate the source noise of detector circuit 340.Source noise is eliminated and required sample and reference photocurrent is balance, and the light absorption that analyte causes can be measured.This is easy to finish, and illustrates in the example below.

For the sake of simplicity, what-if binary gas potpourri.The gas of principal ingredient exists in a large number, and the gas of submember exists with trace.Minimum gas is known as analyte, concern be the amount of Measurement and analysis thing.The binary gas sample mixture is placed sample interaction container 314, pure main gas is placed 334 li of reference interaction volume.Under these conditions, if main gas absorption light, the gas absorption amount is basic identical in sample and the reference substance so.In addition, the amount of the amount of the light that reflects from prism 302,322 interaction surface and the light that absorbed by prism equates for sample and reference beam.Like this, except that the absorption of analyte, the photocurrent on sample detector 310 and the reference detector 330 should keep balance.Thereby the absorption of main gas and the absorption/reflection effect of prism are eliminated, so analyte quantitatively is possible.In addition, in a basic balance because photocurrent keeps, source noise is eliminated.Do not have main gas in reference container 334, the absorption effect of main gas and analytical gas will be arranged from the signal that sample detector 310 obtains, the absorptivity of main gas need be determined in independent test.In addition, do not having to keep photocurrent balance complexity more under the suitable main gas reference.For liquid analyte samples, regulate prism 302 and 322 to allow internal reflection angle greater than 90 °, this just requires additional optics or detecting device 310 and 330 is reorientated, thereby, detecting device can receive with sample and reference interaction after reference beam and sample beam.The output 342 of detector circuit 340 is transferred to computing machine or other control device.Set up internal reflection with the different optical device, can increase sensitivity.The optical devices that produce multiple internal reflectance are more highly sensitive than the optical devices of individual reflection.The feature of Fig. 1 embodiment is suitable for Fig. 3 others, therefore, can improve the sensitivity of internal reflection by the negative effect of restriction source noise and drift.In addition, the general method of eliminating noise among the circuit of Fig. 2 A and 2B and the present invention also can improve sensitivity.

Fig. 4 shows the another kind of modified version of Fig. 1 embodiment, and measuring method is according to direct reflection.Sample beam 400 is injected the smooth reflective interaction surface 402 of wall 404, for example, and catoptron.In interaction surface 402, light and sample interact, and folded light beam 406 is focused on the sample detector 410 by lens 408, and as photodiode, detecting device 410 contains the indoor of ligh trap 411 to be installed in incident light off plumb angle.Detecting device 410 is by signal wire 412 output signals.In Fig. 4, it all is 45 ° to the incident angle of interaction surface 402 with from the reflection angle on surface.Therefore direct reflection has changed 90 ° with the direction of sample beam, can select arbitrarily but this angle is the same with Fig. 3 embodiment.The sample chamber comprises optically transparent closed interaction volume 414, and it comprises as the wall 404 of the part of interaction volume 414 and by wall and sealing.Inlet 416 and outlet 418 allow sample is put into interaction volume 414.Entrance and exit links to each other with the housing of outside, just can fill interaction volume 414 not open this housing.Solid wall 404 is formed a side of interaction volume, makes reflective interaction surface 402 to contact with sample.Special concern be that research is placed on the light absorption of the gaseous substance on the interaction surface 402.

Reference chamber uses similar structure.Sample beam 420 is injected the smooth reflective interaction surface 422 of wall 424, as catoptron.Occur on the interaction surface 422 with the interaction of reference gas (or liquid), reflected light 426 is focused on the reference detector 430 by lens 428, as photodiode, it is installed in the mode identical with foregoing mode and comprises the indoor of ligh trap 431.Reference detector 430 is by signal wire 432 its signals of output.Optically transparent interaction volume 434 is sealed to wall and comprises the part of wall 424 as interaction volume 434.Inlet 436 and outlet 438 allow sample is put into interaction volume 434.Entrance and exit links to each other with the housing (housing shown in Figure 1) of outside, just can fill interaction volume 434 not open housing.

The situation that sample beam may be attenuated is: (i) when passing through the wall of interaction volume 414; (ii) when when being contained in the gaseous sample in the interaction volume; And when (iii) injecting reflective interaction surface 402.The situation that reference beam may be attenuated is: (i) when passing through the wall of interaction volume 434; (ii) when when being contained in the reference gas of interaction volume; When (iii) injecting reflective interaction surface 422.If keep identical gases interaction volume 414 and 434 li, the sample that is absorbed by gas and locular wall and the amount of reference beam are essentially identical so.Aspect absorption, unique possible difference occurs in light beam and injects two different interaction surface 402 and at 422 o'clock.

If (i) sample surfaces 402 has that interactional tendency takes place one or more compositions in very strong and the gas phase, (ii) reference surface 422 is very little with the interactional tendency of gas phase composition, and then Fig. 4 embodiment is particularly useful.For example, the interaction surface 402 of sample that scribbles the polymkeric substance of antibody or special allotment can activate by chemical treatment.Such surface treatment can cause interaction strong between chemical substance and the reflecting surface, and therefore, sample interaction surface 402 can be caught one or more target substances that exist in the gas phase.On reference interaction surface 422, identical material can not be hunted down.If the material extinction on the interaction surface 402, this absorption can be used for detecting and quantizing absorbing material so.

The feature of Fig. 1 embodiment also is suitable for Fig. 4, therefore, and the sensitivity that can improve direct reflection by the adverse effect of restriction source noise and drift.In addition, the conventional method of the circuit of Fig. 2 A and 2B and noise removing of the present invention aspect also can be used for improving sensitivity.The embodiment of Fig. 4 allows to finish the elimination of source noise and the amount of a little light that measurement is maintained at lip-deep material absorbing.Like this, the direct reflection mensuration can be used for monitoring the structure of sample surfaces, can be used to detect and study the physics and the chemical characteristic of the molecular layer of absorption on described surface.

Fig. 5 shows another modification of Fig. 1 embodiment and the method for measuring according to diffuse reflection.Sample beam 500 is injected the matte interaction surface 502 on the wall 504.Light is in direction scope indicated by the arrow scattering.Part scattered light 506 mirror that is reflected focuses on the sample detector 510, and described detecting device is as being installed in the photodiode in the chamber of containing ligh trap 511.The sample detector signal is transferred to signal wire 512.One side of closed sample interaction container 514 is formed by wall 504, thereby, by enter the mouth 516 and the samples of outlet 518 supplies can with interaction surface 502 interactions.

Reference chamber is similarly constructed.Reference beam 520 is injected the matte interaction surface 522 on the wall 524.Light scattering on direction scope as shown by arrows.Part scattered light 526 mirror 528 that is reflected focuses on the reference detector 530, and reference detector 530 is installed in and contains the indoor of ligh trap 531.Reference detector 530 is output signal on signal wire 532.Closed interaction volume 534 is delivered to interaction surface 525 with reference substance and is passed through inlet 536 and outlet 538 supplies.Detector circuit 540 is from signal wire 512 and 532 received signals, and formation output on signal wire 542.In example embodiment, detector circuit 540 is according to Fig. 2 A or Fig. 2 B structure.For example, the output of signal wire 542 can be transferred to computing machine or other control device.

The same with other embodiment, above-mentioned raising sensitivity of method can be used to improve diffusion and measures.In above-mentioned all embodiment, sample and reference detector can be used to produce photocurrent, and it can be handled in many ways to improve sensitivity.For example, the difference of sample thief and reference photocurrent suppresses light source random fluctuation faster.The influence of the more slow drift of peak height light source can by with reference photocurrent compensation recently mutually.Therefore, the type function that provides of formula 3 is quantitative basis in all are used.In the transmission measurement of using the Beer-Lamber law, must use formula 4.For the application of all others, can directly use formula 3, V _D/ V _RAnd the correlativity between analyte concentration is determined with experience.

If be applied on the general purpose instrument, the inlet of chamber, outlet and main body also should be chemically stable to most of organic solvents, yet the instrument scalable of specific use is with the opposing special solvent.The Teflon pad is used for sealing in cell structure.Should filter entrance and exit stops dust in air to enter system.In robot, the flow of gas or liquid can accurately be controlled by control system, and control system can comprise sensor, to monitor for example pressure, flow and the temperature of chamber.Sensor should be carefully chosen, and avoids the thermal effect in the instrument.Clean and filter that the entrance and exit system eliminates that the instrument manufacturing finishes and the dust granule of device generation when being provided with.Afterwards, if sample and reference material are put into by the entrance and exit of suitable filtration, closed system will keep clean.The type of the filtering system of using should be that gas or liquid change according to analyte, but the filtering technique on a lot of market is fit to.

Filtered liquid sample and reference substance have been removed dust and particle.Yet under the situation of liquid, bubble and dissolved gases are owing to may cause that noise also is identified.Another aspect of the present invention is dissolved gases is removed in research from fluid sample a disposal route.This can realize by pre-service that liquid is outgased, for example sonicated before putting into the sample chamber.For fluid sample, preferred disposal route of the present invention is that solvent and analytical solution are outgased.Dissolved gases has been eliminated in the degassing.Usually, when liquid was put into loop system, the bubble in the sample chamber just was not any problem.Yet the degassing also can be removed bubble.

The shell structure of one can provide according to compactness of the present invention, mechanical and heat-staple device, and can be used for the measurement of above-mentioned any kind.Example embodiment will illustrate preferred feature other among the present invention.Fig. 6 illustrates the preferred embodiment of the housing with one.Thermal stability among Fig. 6 embodiment mainly obtains from the solid metal housing 600 of one.Use the high material of thermal conductivity, for example aluminium.For installing and the apparatus for placing element, hollow parts 600a is got out the definite shape and the degree of depth.Solid metal cover board (not shown) seal casinghousing 600, all faces that comprise cover plate of described housing are all isolated.The structure housing 600 of one also provides fabulous mechanical stability.Indoor in compactness, the solid metal housing of one can provide big relatively thermal mass, allows the device littler than the situation among Fig. 1 embodiment.In Fig. 6, optical element be exemplary at interval, and the housing of one allow to shorten the length of light path, and still can reach thermal stability of the present invention.Discovery has thermal drift＜0.005 ℃/minute of the experiment penetrating apparatus of Fig. 6 global feature.

The monochromatic light that sends from monochromator inserts housing 600 by optical fiber 601 and hole 602.Light beam 603 is by collimation lens 604, and collimated light beam 605 produces transmitted light beam 607 and folded light beam 608 with 45 ° of incident angle directive beam splitters 606.Light beam 607 produces transmitted light beam 611 and folded light beam 612 with 45 ° of incident angle directives, second beam splitter 610.Beam splitter 610 is identical with 606.Light beam 611 is caught by ligh trap 613.Equally, light beam 608 produces transmitted light beam 615 and folded light beam 616 with the 3rd identical beam splitter 614 of 45 ° of incident angle directives.With 45 ° of incident angles beam splitter 606,610 and 614 is installed accurately thereby wall 600b is processed.Light beam 616 is caught by ligh trap 617.Here, two-beam 612 should well mate (identical phase place, intensity and polarization) with 615.The layout of this beam splitter obtains at the light beam that be complementary of ultraviolet to far infrared wavelength scope.Light beam is by condenser lens 618 and 619 then, it is in sample chamber and reference chamber focused beam 620 and 621, the sample chamber totally illustrates by 622 and (constitutes the total internal reflection structure according to Fig. 3, comprise surface, closed container, inlet, outlet etc., as shown in Figure 3), reference chamber totally illustrates (constituting the total internal reflection structure according to Fig. 3) by 623.Light beam penetrates from prism 622a and 623a respectively after interacting with sample and reference sample, scioptics 624 and 625 focus on, enter detector compartment 626 and 627, pass through signal wire 630 and 631 with output signal input detector circuit 632 at sensing chamber's detecting device 628 and 629.Beam splitter is preferably mounted on the wall construction 600b of solid metal housing 600.Prism remains in the supporter that is contained on the base plate.This provides the stability of heat and machinery.Another selection is for example to provide intended groove as hollow parts 600a part on wall 600b, so that prism to be installed.Light beam reflects the zone 633 and 634 that enters detector compartment from detector surface, and is hunted down at this.Used three beam splitters to cause the initial light power loss to surpass half in a preferred embodiment.Concrete amount depends on the feature of beam splitter.Be to reduce optical loss, can use separate than be 50/50 (R/T) but the beam splitter of market acquisition.Though loss light, the structure with beam splitter of three couplings has very big advantage, two the bundle emergent lights all has equal power at all wavelength, just, P ₆₁₅=P ₆₀₅R ₆₀₆T ₆₁₄And P ₆₁₂=P ₆₀₅T ₆₀₆R ₆₁₀, reflection R here ₆₀₆=R ₆₁₀=R ₆₁₄, transmission coefficient t ₆₀₆=T ₆₁₀=T ₆₁₄Light beam has identical polarization and phase place in whole wavelength.This has simplified the problem of balance light beam widely.Our preliminary surveying and calculating show, under attainable condition (machining tolerance and commercial beam splitters), much smaller than 0.5%, this enough guarantees source noise is eliminated below the shot noise limit difference of light beam power in entire ultraviolet arrives far wavelength coverage.All shown in figure 2 preferred detector will very well be moved under the light beam of equal-wattage.

As the replacement of three beam splitter configuration, but the mirror prism that in Fig. 6 embodiment, can use market to obtain.Utilize mirror prism, calibration beam is reflected into the light of two bundle equal power from two mirror surfaces of prism.Two-beam departs from 180 °, and therefore, they must become light parallel by two extra direct reflections again.Because light is in summit possibility scattering, so this zone of mirror prism is usually by shading.The power ratio of light beam can be regulated by mobile prism or the hole that suitably is provided with.Yet according to our experiment, we believe the easier generation thermal drift of three beam splitter configuration of this texture ratio.

Another preferred embodiment with solid basically one housing is shown in Figure 7.The embodiment of Fig. 7 is similar to the embodiment of Fig. 6, has solid housing 700, and has the feature of optical stability preferably of Fig. 6 embodiment, solid housing 700 has the hollow parts 700a of placing element and the wall construction 700b of beam splitter is installed, but the same diffuse reflection that utilizes rough surface of Fig. 7 embodiment with Fig. 5.For example, light source 702 is laser instruments among Fig. 7, and it has optical element to produce light beam, and three beam splitter configuration among Fig. 6 obtain by beam splitter 704,706,708.Totally by 710 and 712 expressions, they are according to Fig. 5 structure (with reference to Fig. 5, comprising coarse surface, wall, container, catoptron, inlet, outlet etc.) for sample chamber and reference chamber.

Though illustrated and described each embodiment of the present invention, should be appreciated that for a person skilled in the art, other modification, replacement and change are conspicuous.Under the situation that does not break away from the spirit and scope of the invention that are indicated in the appended claims, can carry out this modification, replacement and change.

In claims, set forth each feature of the present invention.

Claims

1. spectrophotometer comprises:

Seal casinghousing (112,600,700), it does not have internal light source;

Reference chamber (156, Fig. 3-5,623,712), it is installed in the described housing;

Sample chamber (154, Fig. 3-5,622,710), it is installed in the described housing;

Optical system in described housing, the beam separation that is used for externally producing becomes reference beam and sample beam (150,152,300,320,400,420,500,520,620,621), and make reference beam and sample beam pass separately path, and a path is transmitted described reference beam and is entered reference chamber, and another path is transmitted described sample beam and is entered described sample chamber;

Reference chamber interaction device (322,324,434,422,534,522,623a), be used to make reference beam and reference substance to interact, and at least a portion that reflects described reference beam;

Sample chamber interaction device (302,304,414,402,514,502,622a), be used to make sample beam and sample to interact, and at least a portion of reflection sample beam;

Reference light detecting device (330,430,530,629) is used to detect at least a portion by the light of described reference chamber interaction device reflection;

Sample photodetector (310,410,510,628) is used to detect at least a portion by the light of described sample chamber interaction device reflection;

Photoconduction (108,601,702) is used for the light beam that the outside produces is sent to described optical system from light source, and described light source is positioned at the outside of described seal casinghousing.

2. luminosity spectrometer according to claim 1 also comprises sealing assembly parts (110), and it is installed to described photoconduction on the described housing.

3. luminosity spectrometer according to claim 1 also comprises:

Light source (102,702), it is in the outside of described housing, and with described photoconduction optical coupled.

4. luminosity spectrometer according to claim 1 also comprises the selection wavelength device (104,106) with described photoconduction optical coupled.

5. luminosity spectrometer according to claim 4, wherein, described selecting arrangement comprises interference filter.

6. luminosity spectrometer according to claim 1, wherein, described reference chamber interaction device and described sample chamber interaction device all utilize total internal reflection, interact to make reference beam and reference substance respectively, and sample beam and sample are interacted.

7. luminosity spectrometer according to claim 1, wherein, described reference chamber interaction device and described sample chamber interaction device all utilize direct reflection, interact to make reference beam and reference substance respectively, and sample beam and sample are interacted.

8. luminosity spectrometer according to claim 1, wherein, described reference chamber interaction device and described sample chamber interaction device all utilize diffuse reflection, interact to make reference beam and reference substance respectively, and sample beam and sample are interacted.

9. luminosity spectrometer according to claim 1 also comprises dielectric beam splitter (136,606,610,704,706), and the beam separation that is used for that the outside is produced becomes the independently sample beam and the reference beam of outgoing on two light paths.

10. luminosity spectrometer according to claim 1 also comprises:

Detector circuit (189, Fig. 2 A-2C, 340,440,540,632), it receives reference current from described reference light detecting device, receive sample current from described sample photodetector, described detector circuit produces difference current by the current-mode subtraction, then, this difference current is converted into differential voltage, thereby the proportional differential voltage of the difference between generation and reference current and the sample current, described current-mode subtraction makes described reference current of feedback equalization and described sample current on synthetic point

Described detector circuit produce simultaneously differential voltage and with the proportional voltage of described reference current and with the proportional voltage of described sample current at least one.

11. luminosity spectrometer according to claim 10 also comprises passive thermally-stabilised device (112,113,123,135,137,141,154,156,600,700), is used to promote the internal heat balance.

12. luminosity spectrometer according to claim 10, wherein, described reference current is converted into reference voltage, described sample current is converted into sample voltage, described reference voltage and sample voltage carry out subtraction at the input end of differential amplifier, and described then differential amplifier produces described differential voltage.

13. luminosity spectrometer according to claim 12, wherein, described detector circuit also comprises feedback cycle, is supplied to the described input end of described differential amplifier with the fraction with the smaller in described sample current and the described reference current.

14. luminosity spectrometer according to claim 13, wherein, the described fraction of the described smaller in described sample current and the described reference current is to produce about 10 between described sample current and described reference current ^-3Or littler unbalanced amount.

15. luminosity spectrometer according to claim 1 also comprises:

The sample photodetector chamber that holds described sample photodetector;

The reference light detector compartment that holds described reference light detecting device;

Ligh trap (194,196,511,531,633,634), it is placed in in described sample photodetector chamber and the described reference light detector compartment each, to catch respectively by the light of described sample photodetector and the reflection of described reference light detecting device.

16. luminosity spectrometer according to claim 1, wherein, described housing comprises having hollow parts (600a, the solid metal housing of one 700a) (600,700), described hollow parts is formed, and installs and place described reference chamber, described sample chamber, described optical system, described reference light detecting device and described sample photodetector to provide.

17. luminosity spectrometer according to claim 16 also is included in the groove in the solid metal housing of described one, is used to keep each parts of described optical system.

18. luminosity spectrometer according to claim 16, wherein, the solid metal housing of described one comprises aluminium.

19. a luminosity spectrometer comprises:

The housing of solid basically heat conduction (600,700);

Hollow parts in described housing (600a, 700a), it limits optical communication path and component locations;

Light well (602), itself and described hollow parts optical communication;

Collimation lens (604,702), itself and described light well optical communication;

First beam splitter (606,704), itself and described collimation lens optical communication;

Second beam splitter (610,706), the transmissive side optical communication of itself and described first beam splitter;

The 3rd beam splitter (614,708), the reflection side optical communication of itself and described first beam splitter;

An optical communication in reference chamber reflective interaction interface and the folded light beam detection system (623,623a, 712), itself and described second beam splitter or the 3rd beam splitter;

Another optical communication in reflective interaction interface, sample chamber and the folded light beam detection system (622,622a, 710), itself and described second beam splitter and the 3rd beam splitter.

20. luminosity spectrometer according to claim 19, wherein, the reflection side of described reference chamber reflective interaction interface and folded light beam detection system and reflective interaction interface, described sample chamber and folded light beam detection system and described second beam splitter and the transmissive side optical communication of described the 3rd beam splitter.

21. luminosity spectrometer according to claim 19, also comprise ligh trap (613,617), it forms the part of described hollow parts, and is arranged to catch by the light beam of the second beam splitter transmission with by described the 3rd beam splitter beam reflected.

22. luminosity spectrometer according to claim 19 also comprises additional ligh trap (633,634), to catch the reflected light from described reference chamber detection system and sample chamber detection system.

23. luminosity spectrometer according to claim 19, wherein, described reference chamber reflective interaction interface and folded light beam detection system and reflective interaction interface, described sample chamber and folded light beam detection system include:

Prism (302,322,622a, 623a), it has interaction surface (304,324);

Detecting device (330,310,628,629);

Lens (308,328,624,625) are used for the light beam from described prism output is focused on described detecting device;

Closed interaction volume (314,334), it has entrance and exit, so that gas or liquid are sent on the interaction surface.

24. luminosity spectrometer according to claim 19, wherein, described reference chamber reflective interaction interface and folded light beam detection system and reflective interaction interface, described sample chamber and folded light beam detection system include:

Reflective interaction surface (402,422);

Detecting device (430,410);

Lens (408,428) are used for the light beam from described reflective interaction surface output is focused on described detecting device;

Closed interaction volume (414,434), it has entrance and exit, so that gas or liquid are sent on the reflective interaction surface.

25. luminosity spectrometer according to claim 19, wherein, described reference chamber reflective interaction interface and folded light beam detection system and reflective interaction interface, described sample chamber and folded light beam detection system include:

Coarse interaction surface (502,522);

Detecting device (530,510);

Lens or catoptron (508,528) are used for the scattered light from the surface output of described matte interaction is focused on described detecting device;

Closed interaction volume (513,534), it has entrance and exit, so that gas or liquid are sent on the interaction surface.

26. a luminosity spectrometer comprises:

The housing (112,600,700) of sealing, it does not have internal light source;

Optical system in housing, the beam separation that is used for the outside is produced is reference beam and sample beam (150,152,300,320,400,420,500,520,620,621) and transmit reference beam and sample beam and pass separately path, a path transmission reference beam enters described reference chamber, and another path transmission sample beam enters described sample chamber;

Reference chamber reflective interaction interface and folded light beam detection system (322,324,434,422,534,522,623a), itself and a path optical communication transmitting reference beam;

Reflective interaction interface, sample chamber and folded light beam detection system (302,304,414,402,514,502,622a), itself and another path optical communication of transmitting sample beam;

Sample photodetector (310,410,510,628) is used to detect at least a portion by the light of described sample chamber interaction device reflection; And

Photoconduction (108,601,702) is used for the light beam that the outside produces is sent to described optical system from light source, and described light source is positioned at the outside of the housing of described sealing.

27. luminosity spectrometer according to claim 26, wherein, described reference chamber reflective interaction interface and folded light beam detection system and reflective interaction interface, described sample chamber and folded light beam detection system include:

Prism (302,322,622a, 623a), it has interaction surface (304,324);

Detecting device (330,310,628,629);

28. luminosity spectrometer according to claim 26, wherein, described reference chamber reflective interaction interface and folded light beam detection system and reflective interaction interface, described sample chamber and folded light beam detection system include:

Reflective interaction surface (402,422);

Detecting device (430,410);

29. luminosity spectrometer according to claim 26, wherein, described reference chamber reflective interaction interface and folded light beam detection system and reflective interaction interface, described sample chamber and folded light beam detection system include:

Coarse interaction surface (502,522);

Detecting device (530,510);

30. luminosity spectrometer according to claim 26, wherein, described housing comprises:

The housing of solid basically heat conduction (700,600);

(700a, 600a), it limits the communication path and the component locations of light to hollow parts in described housing.